Abrasive block or segment



y 1951 A. s. TITCOMB Re. 23,364

ABRASIVE BLOCK 0R SEGMENT 5 Sheets-Sheet 1 Original Filed June 1, 1949 W IMQIMHWIH INVENTOR. J/Jerffepara 72100106 BY flaw/13M ATTORNEYS.

y 1951 A. s. TITCOMB Re. 23,364

ABRASIVE BLOCK OR SEGMENT Original Filed June 1, 1949 5 Sheets-Sheet 2 INVENTOR.

J/b 8/! Shepard 73:10 amb A T TORNEYS.

y 1951 A. s. TITCOMB Re. 23,364

ABRASI VE BLOCK 0R SEGMENT I Original Filed June 1, 1949 5 Sheets-Sheet 3 214/ 2/1 Jay/9.

INVENTOR. fl/berf Jep aral 7Zz'lc 0m 19 ATTORNEYS M y 8, 1951 A. s. TITCOMB Re. 23,364

ABRASIVE BLOCK 0R SEGMENT Original Filed June 1, 1949 V 5 Sheets-Sheet 4 185.910 AE/MJ/VLC ATTORNEYS IN V EN TOR.

y 1951 A. s. TITCOMB Re. 23,364

I ABRASIVE BLOCK 0R SEGMENT Original Filed June 1, 1949 5 Sheets-Sheet 5 A TTORNEYS- Reissued May 8, 1951 UNITED STATES PATENT OFFICE rial No. 96,476, June 1, 1949.

Application for reissue'October 31, 1950, Serial No. 193,231

Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

22 Claims.

This invention relates to an abrasive grinding wheel which is composed of a plurality of spaced abrasive surfaces, and more particularly to the abrasive block or segment which is utilized for such a wheel. This application is a continuationin-part of my co-pending application Serial No. 679,807, issued July 19, 1949, Patent Number 2,476,334, which claims more particularly the wheel as a whole, while this application is directed specifically to the segment or block per se which goes into such wheel.

Abrasive grinding wheels of the above character have heretofore been constructed of a grinding segment composed of abrasive material shaped like a hollow cylinder, known in the trade as an inverted cup. The sides of the cup are often made of segments each looking into the next segment [or sometimes by segments with spaces in between with looking devices to hold the sides of the cup to the upper base of the grinding wheel by means of what is known in the trade as a chuck.] This and all such segments are possessed of convex or concave blunt ends.

Sometimes the sides of the cup are made of segments with spaces in between the segments, and these are held by a locking device which retains thesides of the cup to an upper base by means of what is known in the trade as a chuck, and such segments are also usually formed with blunt ends as hereinafter described.

Still another style of segment is so constructed and spaced in a chuck that it will conform to the circular outer surface of a cup wheel while the inner surface of each segment is fiat and the complete wheel, due to the several flat inner surfaces of the segments assumes a prismatic inner form.

Such segments are generally considered by the trade and by. me to have sharp ends, and they are, as we use the term, sharp ends. In actual practice they are not, as we use the term hereinafterexplained, full sharp ends, since these otherwise full sharp ends are modified at the tips by a cut at right angles to the flat inner surface, thus decreasing jragility and assuring proper fit in the chuck that is made to hold them. Any such [This] wheel is intended for operating on a mounting at the bottom of a rotating vertical spindle on work fastened to a movable base (either rotary or reciprocative) and where the revolving segments are pressed downward against the work. It is also intended for operating on a mounting at one end of a horizontal spindle 9, Work fastened to a reciprocating table so 2 that the revolving segments are pressed against the work. When the wheel is applied to the work, chips of the work and also of the cutting wheel are formed by removal of the stock of each. This removed stock will load up or interfere with the eflicient cutting action of the usual types of wheels, the cutting efiiciency of a wheel depending to a substantial extent upon the elimination or removal of this debris. Thus, the particular shape of the block and arrangement of the several blocks in the wheel are there'- fore very important from the standpoint of an efficient cutting wheel. It has been found that if this loose stock is readily removed from the grinding before it becomes embedded into the cutting surface of the wheel or segment, it is unnecessary to dress the wheel as frequently as otherwise and even often eliminates such dressing entirely. This is because the loose stock fillsin the crevices, that is, loads the wheel so that the cutting edges of the rough surface are neutralized and forms a smooth uncutting wheel which causes heating, burning, and warpage of the work being'ground. This friction instead of cutting action often causes sufficient friction to throw the work off the magnetic chuck, generally used, sometimes with serious results.

One of the objects of this invention is to provide a block for an abrasive grinding wheel, which block will be of such shape that it will provide a more efficient and freer cutting wheel action than [similar] other segmental block wheels have heretofore accomplished.

Another object of this invention is to provide 1 a shapeof abrasive block so that chips will be self-removed efliciently and thus prevent loading of the wheel.

Another objectof this invention is to provide an abrasive block which will cause its leading edge to have an efficient plow action upon the chips which are formed to spread the chips outwardly and inwardly 01' the [wheel as the cutting surface of the block] block, maintaining clean, the cutting surface of the block as it advances.

Another object of this invention is to provide an abrasive block which, when in a wheel, will run 0001 and free of loading and thus prevent heating and warping of the work.

Another object of this invention is to provide an abrasive block which will be of such form that it may be utilized in a plurality of different diameter wheels, thus enabling lower cost to manufacture through [the standardization and also greatereconomy in cases where there is need of replacement through damage] this standardiza 3 tion by necessitating the use of only a single mold in connection with the manufacture, and only a. single style of segment in inventory for servicing. and supplying such a wide variety of diameters and types of chucks for the many sizes and makes of grinders.

With these and other objects in View, the invention consists of certain novel features of construction, as will be more fully described and para ticularly pointed out in the appended claims.

In the accompanying drawings:

Figure 1 is a perspective view of an abrasive block formed in accordance with this invention;

Figure 2 is a plan view of several of the abrasive blocks arranged in the form which they will assume in a grinding wheel utilizing abrasive blocks of this shape; alsoshown is the path of the work obliquely across the face of the. segment as it rotates about the center with the chips for the greater part coming 01? the inner side of the se ment and being f r i y struck y the ute side of the succeeding segment, thus plowed outwa div n disp d f.

Figure 3 is a diagrammatic view of the basic form of a segment or block having rather ideal plow-like properties when in action if the same we e drawn in a str i h line;

Fi re. 4 is a view. similar to Figure 3, but illustrating the se ment as being developed into an arcuate form or shape desirable for grinding Wheel p rpos Figure 5 a plan view of a block illustrating a modified shape so far as Figure 4 is concerned, but. showin dia rammatically y m ns of radius lines ne haping of the block f manufacturing purposes such as is shown in Fi re 3.;

Figure 5 -a is a plan view and is an exact copy of the sh pe of he segment as shown in Figure 4 of U. .5. Patent No. 2,476,334, of which this application is a continuation-in-pdrt case, and illustratesihe end of segment wherein the inner contour is subject tov abrupt changes in direction, thus causin the segment to have an angular median.

- Figure 5.b is a plan view and illustrates the right end'of a, segment identically like Figu e. 5. except that it is in line with actual manufacturmy practice. The substantial portion of each of the converging sides of the end of the segment are identical with those. of Figure 5., except that the tip of this segment shows an arc of substan tial size which may or may not. be of regular. contour (in fact, more often not) in that these segments are. made of abrasive material.

Figure 5-.c is a. plan view and illustrates a flg-M are identical to Figure 5 except that, as in Figure. 5.x-a, an abrupt change in the. inner contour occurs where a curve of lesser radius causes the, segment to be of thinner. construction, thus effectively reducing the area and producing a softer grinding action. with a. given grade of specification.

Figure 7 is a diagrammatic view illustrating a segment formed from two arcs;

Figures 8, 9, 10, 11, and 12 are diagrammatic Views each showing an inner edge of any suitable iarcuate form [having aysi'ngl arc,] while the outer surface of the segment is formed arcuate each of difierent form by different formations of the surface;

Figures '13 to 16 [and 18] are diagrammatic views illustrating segments each of modified form and showing the inner surfaces of the segments each different but formed from fiat and curved surfaces of varying form although generally of the same characteristics; [and] while the outer surface of the segment is of any suitable arcuate form.

Figure 17 illustrates a segment which is substantially one-half of the segment shown in Figure 1, the outer surface XZ being of longer extent than the inner surface XY.

Figure 18 is a plan view and illustrates a segment, in which both the inner and outer arcuate surfaces are made up of a series of plane surfaces, each substanlially flat or only slightly arcuate, and set at obtuse angles one to another. Also shown is the resultant angularly arcuate median.

Figure 19 is a diagrammatic view illustrating.

the meaning of certain definitions, or terms used in this specification and includes diagrammatic material of prior art for reference thereto.

In proceeding with this invention, I have constructed an abrasive block or segment of an elongated shape which will have substantially pointed ends. The leading pointed end will be so positioned in the wheel that the opposite flaring edges from the leading end will have a plow action upon the chips and debris [removed] ground of? by the preceding segment [.1 or segments. The greater part of this action is accomplished by the outer side, for as the work cmsses the segment obliquely, most chips come 017 the inrver edge of the cutting surface, mix with the coolant, and are struck by the outside of the succeeding segment, thus said outer side forces these :chips outwardly. by physical displacement (plowing action) plus centrifugal force.

These blocks are all of the same size and shape for standardization and for grinding wheels of difierent diameters, and I usually mount more upon a larger wheel than on a smaller wheel in order to provide the size of grinding wheel desired. blocks may also be arranged in overlapping circular echelon relation so that a continuous cutting Surface is provided on the work, thus preventing the opportunity for the stock being ground to rise, and at the same time pro-. viding. necessary chip clearance between blocks or se ments. The overlapping; relation will be so spaced that the chips removed fromthe work may be thrown aside. from the wheel by centrifugal force.- as well as by physical displacement of the plow action referred to above. Coolant is usually delivered at a location just inwardly of the. circular cutting annulus of the wheel and flows to the work surface within this annulus. For greater detail concerning the wheel itself, reference is made to the above-mentioned copending application (U. S- Patent No. 2,476,334).

-By the general term arcuate I mean a line which may be shaped like the bow of a bow and arrow and formed of portions of several true arcs struck from centers; or .a line which may be. formed of flat surfaces. at obtuse. angles to each other and polygonal in plan or a line made up of, arcs and flat surfaces generally in'the form of the median line or either edge depicted in the various views.

By the specific term angularly arcuate I mean specifically a line which is shaped, taken as a whole over its length, like the bow of a bow and arrow, and formed of flat surfaces, joining at obtuse angles to each other of non-blending contour and polygonal in plan, or a line formed by arcs or arcuate and flat surfaces joining at obtuse angles to each other of non-blending contour, generally in the form shown by the outer edge depicted in Figures 10, 11, and 12, and on the inner edge as depicted in Figures 5-a, 5-0, and 5-d, 14, 15, 16, or both edges and the median in the Figure 18.

By the specific term non-angularly arcuate, I mean a line which is shaped like the bow of a bow and arrow, and formed by portions of several true arcs struck from centers or formed by arcs or arcuate and flat surfaces, all such arcs or arcuate surfaces joined with flat surfaces blending tangentially to form a smooth, unbroken continuity as depicted by either edge or the median in Figures 1, 2, 3, 4, 5, 5-b, 6, 7, and 17, or the outer edge of Figures 5-a, 5-c and 5-d.

It is here recognized that any figure, to have a non-angular median must have both of its sides of non-angular form. One side of angular form will cause an angular median which will average in the extent of its angularity between the angle of the angular side and the side of smooth nonangular contour.

By the term blunt end, I mean the end formed on the e tremity of two relatively long parallel surfaces, as Fig. 19, 203 and 204; or an end formed on two concentric surfaces as 201 and 202, as a portion of a cylinder; or an end formed on the outer extremity of two diverging surfaces of a solid object, said ends being bounded either by a semi-circle, as 205, or any cords of a semi-circle, as 206 and 207, from a point along said semi-circle to said surfaces.

By the term sharp end, I mean the approach, one toward another, of two converging surfaces, as 210 and 211, of substantial length with relation to full size of the object, regardless of whether the tip may be an are substantially blending into the two said converging surfaces, as 212, or a flattened tip as 213, or any other formation of structure, as of abrasive material, convenient and practical for manufacture, causing said terminating end surface.

t is here recognized that theoretically, the sharpest end is formed by the intersection of two surfaces that are just 017 of parallel. For the purpose of this patent, the opposite extreme of sharpness toward bluntness shall be considered the joining by any method of the two converging surfaces of substantial relative length, the included angle through which would be less than 90. See Figure 19, 210 and 211, compared with 206 and 207.

By the term full sharp end, in contra-distinction to the above definition of sharp end, I mean to indicate the full continuation of each surface to the theoretical point of intersection 214, and as shown all of my figures, the single exception of Figure 5-b, which compares with 212.

The fact is, that blunt, sharp, and full sharp are relative terms, and are necessarily limited by the application of the product. With any mechanical cutting device the sharpest edges under sufiicient magnification show definite roundness.

As used in my claims the term sharp is used essentially to differentiate between the converging, acutely angled, sides forming the ends of my segments and the concentric non-converging inside and outside full length surfaces, or sides, of other shapes of segments, including in particular that type upon which an arc of substantially full semi-circular character forms an end, as 205 on 201 and 202, considered by me, and, as would be defined above, as a blunt end. In contrast, the converging ends of my segments form what -I consider a sharp end, looking at the segment as a whole, regardless of the actual condition of the tip, where an arc, joining the converging sides of my segments, tangentially, would always form only a portion of and definitely less than a full semi-circle. Therefore, the joining in any manner convenient for manufacture of the converging sides of my segments, as with other typical segments, as one formed by 201 and 204 theoretically ending in 215, but actually as manu-, factured ending at 216, and thus comes under the meaning of sharp ends.

In Figure 19 I have shown the ends of some forms of hypothetical segments for the purpose of defining exactly what I mean by the terms blunt end, sharp end, and full sharp end.

Lines 201 and 202, which may be concentric arcs or straight surfaces, as 203 and 204, extending parallel to each other, illustrate the side-edge surfaces of the center portion of a body, typical of a segment. 1

When said side edge surfaces are tangentially joined to each other by a semi-c rcular are 205, an end is formed which I consider to be a blunt end.

When said side edge surfaces are joined by any two straight converging end surfaces, as 206 and 207, which are based at the ends of the, semicircle 205 and which, if converged to their ape.v said apex meeting on the semi-circle 205-such converging ends would approach one another at an included angle, which must necessarily be which I consider to be a blunt end.

When said side edge surfaces are joined to each other by any end surfaces as 208 and 209, which. would be contained within the semi-circle, they form a greater obtuse included angle condition than the 90 condition described above, which I also consider to be a blunt end.

When said side edge surfaces are joined by surfaces similar to end surfaces 208 and 209, by slightly changing the relative position, hinging at the inner side, so that 209 comes to a radial position relative to the wheel as a whole, becoming as 219, while 208 becomes as 218, said type of segment also possesses what I consider to be a blunt end.

When said side edge surfaces are joined to each other by any end surfaces of substantial extent as 210 and 211, which if converged to their apex would meet outside the semi-circle 205, such converging end surfaces will make an acute angle condition rather than the 90 condition described above and would therefore provide what I consider a sharp end regardless of the extreme I In Figure 19, when one end of a segment is formed as having the outer surface 201, the in:

mer surface 204, said segment while theoretically ending in point 215 is actually modified in praetice by 21.6, forming at'216 what is termedhere a sitar-pend An arcuate surfa'ce*-oj greater radius means neareraflat surface and of lesser "radius would mean further froma fiat -surface.

IZA "line of less -'-curvatu-re means nearer a straight line and greater or sharper curvature wofildmean furtherfrom a straight line-J With reference to 'the' 'drawings' Figure' 1 hows 'ai perspective view or an abrasive block or segment -90 of a commercial form which is the subject of this invention. Four of such blocks-are shown in' Figure 2 in" the arrangement which will *occurw-hen assembled-as an-abrasive wheel indicated-Lby dot and da'sh lines BI. 'Ineachcase the leading end 92 of the b1ock-wi11 be nearer the -="center of -the wheel than the trailing end -93 so-as to -arrange the blocks -ina circular eche- 1on relation with the leading end of one block usua'lly overlapping the trailing-end ofthe next block so that engagementwith' the-work" [is] may be continuous.

Figure 2 also illustnates the pla'th of the work with respect to the centerof rotation of-the wheel, clearly indicating the oblique-passageof such work across the face of my segmentswhen position in -my'chuck. Tlhe'pdth of debris or chips will be traced to'the inner'e'clge of the cutting segment for the most -part, whence it passes fromthis' inner-edge, mixes with the coolant, if anygand is struck by-the outeredge of the succeeding segment, thus being plowed-away. At

this point, also,- centrifugal force comes into play i v and "has the very desirable effect of maintaining clean the'outer plowing surface ofmy segments.

In Figure 3 I have illustrated at I00 a fundamental 'form of abrasive block which will have pointed ends'IIII formed by reducing the thickness from the extreme width along a substantial length. As most grinding wheels are formed in circular shape, the'abrasive block which'willbe used will be of arcuate shape and wi11- be- "developed from the l fundamental ="form' shown in Figure 3 by determination of thegeneral curvature of the block desired --which may be the median line a or center line of the --block I02 from-"which the shape-is developed. Figure 4 designates such median line with the opposite edges layed oil on either side of the median line as equal dimensions along radii I02 from'the center of the median 1ine,'or ifthis-mediarr line is nota true are having a-center but is'rather arcuate'in form, the layout will be'along lines' at right angles to the portion of the arcuate line at different points along its length. 'In 'Figure4 the inside arcuate edge of the block is shown to have a reverse curve I03 as it approaches the median line to form an acutely angled end.

'A form which is foundto be suitable is shown in Figure 5 where the medianline IIlII'is-formed on the arc of a circle having a radiusIIJE, while the-inner and outer edges of the block are arcuate, the outersurface having acenter-arc from radius I06 with arcs from-shorter radii at each end such as IO'I joiningthe center arcto the median line at I08. -The inner'edge ofthe block is also arcuatehaving a center arc from radius I09 which is connected by-straight'lines such as I III to the ends' I 08 which are on the median'line. A .perspective a view of i the block so-formed is shown in Figure 1. In each case; however' acutely angled. ends are provided[.];"-ju'll sharpends being generally s showin s nearly such jilll sharp'ends as possible will secure maximum performance through-obtaining the maximum plowing action.

In Figure '5-a I have shown an exact ccpy' of the shape of the segment as shown in Figure-4 of the'U.-S. Patent No. 2,476,334, of which this patent is a c ntinuation-in-part. Here the median will be seen to have an angular break as at 150 and-151, inherent therein due to the abrupt change in the direction of the inner edge from 152 asat 153 and 154. This is inherent in the structure.

In Figure 5-b I have shown the right end of a segment identically like Figure 5, except that it is inline with actual manufacturing practice. The substantial portion of each of the converging sides-.155 and 156 of the end of the segment are identical with those of Figure 5, except that the tip 157 of this segment shows an arc ofsub'stantial size which may or may not be of regularcontour, in fact more often not, in that these segments are made of abrasive material which is of rough character. This cannot help but occur in varying degree in actual manufacturing practice.

InFigure 5-c I have shown a figure identical to Figure 5 as far as the important bearing'or land areas used in actual manufacture are concerned, but, as in Figure 5-a an abrupt change of the inner contour occurs at .158 where a curve of lesser radius 159 at the inner center joins the fiat inner land end, portion 160, thus efiectiuely reducing the area in the same manner as would be standard practice for ring-wheel operation, in that the cutting edge of the wheel is thinned down. The resultant angularly arcuate median line 161 is also shown.

In Figure 5-d I have shown a figure identical to Figure 5 as far as the important bearing or land areas used in actual manufacture are concerned, but, here I have in effect a repetition of a practical application of our Figure herein, thus having the exact opposite effect to Figure 5-c in that it increases, rather than decreases, to the desired extent, the area of the segment grinding on the work. Median line162 is included.

In some cases, as shown in Figure 6, there may be a single inner. are for the inner surfaceof the block which is designated H2 and struck from the radius H3, while the median line may bean arc H4 having radius H5 with the outer surface H6 arcuate and formed from arcs having radii H7 and other radii I I8 of shorter radius at the ends, thus forming acutely angled ends H9. In some cases I may provide a segment formed of two arcs, as shown in Figure 7, there being an inner arc I formed on radii I2I and an outer arc I22 formed on radii I23, thus also providing acutely angled ends I24 but of a much thinner and more fragile character.

In 'Figure 8 I have shown an inner surface formed from a single arc I25, while the outer surface I is formed arcuate having-arcs I27 at either end joined by a flat portion I28 which may be raised as at I28 toprovide a land to fit the contour of the holder for mounting the segment, which land may be an alternate form to'that shown in my Patent 2,476,334 in Figure 5 at 31. In Figure 9 I have shown the inner surface I29 formed: from an arcof a single radius, while the outer surface I is formed from a plurality of flat surfaces I3I each in an obtuse angle to each other but generally conforming to the shape-defined in- Figure 6. InFigure 10 the same general arrangement, as shown in FigureQ, is provided,

9 there being an arc of uniform radius I32, while the outer surface I33 is formed from a plurality of flat surfaces I34 longer than the fiat surfaces I3I and each at an obtuse angle to the next one but all generally conforming to the shape of the arcuate surface II6 of Figure 6.

Modifications of the outer surface of the segment are shown as in Figure 11, there being a curved middle portion I35 joined by three flat surfaces I36, I31, and I38 to form the end portion of the block, while in Figure 12 the outer surface is composed of an arc I35! joined by a single flat surface I40 at either end of the block to connect with the inner surface of the block.

The inner surface of the block may also be formed arcuate in several different forms and these are shown in Figures 13, 14, 15, and 16. In Figure 13 the inner surface is formed from a plurality of short flats HI each at an obtuse angle to each other, while in Figure 14 there are longer flat surfaces I42 connected by shorter flat surfaces [I48] 143 each at an obtuse angle. In Figure 15 three fiat surfaces are provided, there being a middle flat surface I and end flat surfaces I45, while in Figure 16 two fiat surfaces I46 are provided meeting at the center I41.

The above blocks all provide practical schemes of forming blocks which may be disposed in the circular relation which is shown in the wheel of Figure 2, it being merely necessary to utilize one of these many forms for many wheels of different diameter which may be desired. The holders for the blocks or clamps will, of course, be uniform and of a shape to cooperate with the particular shape of block desired. From a strength characteristic standpoint it is desirable to have the ends of thicker or heavier section in order that they may be stronger and the form which I have shown in Figures 1, 2, and is found to be the more suitable in this regard rather than the more fragile section of Fig. '7. The many forms illustrated, however, indicate the variations which may be adopted and combinations of which come within the purview of this invention.

In Figure 17 I have shown a block 95 which is substantially one-half of the block shown in Figure 1, which in some cases it may be desirable to use. It will be noted here that the outer surface of this figure, as on all of my segments, is of longer extent than the inner surface: X-Z is longer than XY. It will also be noted that the median 96 is not angular.

In Figure 18 I have shown a block, both the inner and outer surfaces 163 and 164 of which are made up of a series of plain surfaces set at obtuse angles forming angularly arcuate sides. The median 165 reflects this angularly arcuate condition in that it is also angalarly arcuate.

I claim:

1. A bonded abrasive block shaped as a pseudo hollow cylindrical segment, formed between [two arcuate surfaces] an inner arcuate surface of shorter and an outer arcuate surface of longer extent, said arcuate surfaces being perpendicular to an end surface and substantially equidistant throughout their course from [an] a nonangular arcuate median, said inner and outer arcuate surfaces meeting at said median in an acutely angled substantially sharp end.

[2. A bonded abrasive block as in claim 1 wherein one of said arcuate surfaces comprises an arcuate surface merging into a flat plane carried to the arcuate median] 3. A bonded abrasive block as in claim 1 wherein said inner surface comprises an [arcuate sur- 10 face] are merging into a flat plane carried to [the] saidarcuate median.

4. Abonded abrasive block as in claim 1 wherein one of said surfaces comprises an arc merging into an arc of shorter radius intersecting said median.

5. A bonded abrasive block as in claim 1 wherein said exterior surface comprises a mid arc merging into an arc of shorter radius intersecting said median.

6. A bonded abrasive block as in claim 1 wherein one of said surfaces comprises a fiat surface merging into [modified by] an arcuate surface intersecting said median.

7. A bonded abrasive block as in claim 1 wherein said exterior surface comprises a flat surface merging into [modified by] an arcuate ,surfac intersecting said median.

8. A bonded abrasive block as in claim 1 where'- in said inner surface is modified at its acutely angled end through a merging of the interior arcuate surface into an arcuate surface of reverse direction carried to said median.

9. A bonded abrasive block as in claim 1 wherein said opposite ends are symmetrical with reference to the mid point on the median. t

10. A bonded abrasive block shaped as a pseudo hollow cylindrical segment [of symmetrical form] comprising leading end, center portion and trailing [portions] end, said center portion being formed between inner and outer generallyarcuate surfaces, both perpendicular to an end surface said leading and trailing portions being symmetrical and meeting in acutely angled sharp ends formed through modifications of at least one of said inner and outer arcuate surfaces] and each respective leading and trailing end being similar and formed by converging continuations of the inner and outer arcuate surfaces of said center portion into substantially sharp ends.

11. A bonded abrasive block as in claim 10 wherein one of said arcuate surfaces merges into a fiat plane carried to said end.

12. A bonded abrasive block as in claim 10 wherein said inner arcuate surface merges into a fiat plane carried to the said end.

13. A bonded abrasive block as in claim 10 wherein one of said arcuate surfaces merges into an arc of shorter radius carried to said end.

14. A bonded abrasive block as in claim 10 wherein said [exterior] outer surface comprises a mid arc merging into an arc of shorter radius carried to said end.

15. A bonded abrasive block as in claim 10 wherein said inner arcuate surface is modified at its acutely angled end through a merging of the interior arcuate surface into an arcuate surface of reverse direction carried to said end.

16. A bonded abrasive block as in claim 10 wherein one of said surfaces comprises a flat surface [modified by] merging into an arcuate surface carried to said end.

19. A bonded abrasive block, as in claim 1,

wherein said exterior surface comprises a midarc merging into an arc of shorter radius intersecting said median, and wherein said opposite ends are similar.

20, A bonded abrasive block, as in claim 1, wherein said inner surface comprises an arcuate surface merging into a flat plane, carried to the arcuate median and wherein said outer surface comprises a mid-arc merging into an arc of shorter radius, intersecting said median,

21. A bonded abrasive block, as in claim 1, wherein said inner surface comprises an arcuate surface merging into a flat plane, carried to the arcuate median and wherein said outer surface comprises a mid-arc merging into an arc of shorter radius, intersecting said median, and wherein said opposite ends are similar.

22. A bonded abrasive block shaped as a pseudo hollow cylindrical segment, of symmetrical form with reference to the mid point on the median formed between an inner arcuate surface of shorter, and an outer arcuate surface of longer extent, said arcuate surfaces being perpendicular to an end surface and substantially equidistant throughout their course from an arcuate median, said inner and outer arcuate surfaces meeting at said median in an acutely angled sub- 25 Number stantially sharp end.

ALBERT SHEPARD TITCOMB.

REFERENCES CITED The following references are of record in the file of this patent or in the original patent:

UNITED STATES PATENTS Number Name 7 Date 15 797,427 Harris Aug. 15, 1905 848,760 Mills Apr. 2, 1907 1,027,536. Gardner May 28, 1912 1,767,321 Skillings June. 24, 1930 1,868,492 Buckeister July 26, 1932 20 2,082,404 Leshure June 1, 1937 2,235,446 Birger et a1. Mar. 18, 1941 2,307,632 Meyer Jan. 5, 1943 FOREIGN PATENTS Country Date 52,589 Switzerland July 15, 1910 

